1. Field of the Invention
The present invention relates to a display apparatus, in particular to a display apparatus adapted to be capable of rotating a screen by 90.degree. so that a picture on the screen may match both a longitudinally long form and a sideways long form made by a word processor and the like and the screen may be tilted in accordance with a direction of operator's eyes.
2. Description of the Prior Art
A CRT display unit, which is side ways long to an extent of an aspect ratio of usually 3:4, has been used as a display apparatus. Accordingly, when a longitudinally long document, which is usually used, is made by a word processor, a problem has occurred in that the wastefulness is very large since a screen of the display unit of a word processor is sideways long.
In addition, when the display apparatus is placed on a desk, the screen has become difficult to be seen according to a physique of an operator, more concretely to a direction of the operator's eyes changed due to a height of the eyes.
In order to solve such problems, U.S. Pat No. 4,267,555, Japanese Utility Model Publication No. 40-13050 (1965), Japanese Utility Model Laid-Open No. 47-10420 (1972), Japanese Utility Model Laid-Open No. 48-41118 (1973), Japanese Utility Model Laid-Open No. 60-62155 (1985), Japanese Utility Model Laid-Open No. 50-124223 (1975), Japanese Utility Model Laid-Open No. 59-149190 (1984) and the like have been proposed.
According to U.S. Pat. No. 4,267,555, a screen of a CRT is adapted to be capable of rotating by 90.degree. relatively to a back unit by combining a front unit provided with a CRT with the back unit provided with a display yoke by means of an annular thrust bearing. However, in this invention since the annular thrust bearing is used, problems occur in that the display unit is increased in weight, the installation of the display unit requiring a comparatively large space, and also the assemblage of the display unit being complicated.
According to Japanese Utility Model Publication No. 40-13050 (1965), a rear end portion of a front unit carrying a CRT is adapted to be engaged with an opening formed on a front face plate of a back unit to be supported by an edge of a front face plate of the back unit cabinet and capable of being rotated. However, a problem occurs in that a cabinet plate must be thick in order to gain a sufficient constructive strength for supporting the front unit carrying the CRT having a considerable weight by the back unit, whereby increasing the weight.
According to Japanese Utility Model Laid-Open No. 47-10420 (1972), a cabinet, which is formed in a cylindrical shape, is adapted to be rotated with being put and supported in an annular supporting frame. However, according to the present device, the cabinet is increased in size exceeding the necessity, whereby increasing a weight coupled with the annular supporting frame. In addition, since an antenna wire, a power source wire and the like drawn out from the cabinet are rotated together with the cabinet, there is also the possibility that they are disconnected due to the twisting.
According to Japanese Utility Model Laid-Open No. 48-41118 (1973), a disk, which is mounted on a front end surface of a CRT, is adapted to be put in a hole formed in a front end of a cabinet to be rotated. However, a construction for bearing a weight of the CRT is not taken into consideration in the same manner as in the above described Japanese Utility Model Publication No. 40-13050 (1965).
According to Japanese Utility Model Laid-Open No. 60-62155 (1985), a middle portion in the longitudinal direction of a cabinet formed in a cylindrical shape is adapted to be supported by a roller mounted on a supporting arm, pivoting a center of a rear end portion of the cabinet thereon. With such a construction, although a weight of a CRT can be sufficiently born, the cylindrical portion of the cabinet is merely laid on the roller. Accordingly, a problem occurs in that the cabinet is not surely held by the supporting arm.
According to Japanese Utility Model Laid-Open No. 50-124223 (1975), a picture of a television receiver is adapted to be rotatable around a horizontal axis of shaft line and a vertical axis of shaft line relatively to a base table. Concrete constructions thereof, in which a spherical cabinet housing a CRT thereinside is placed in a dented portion of the base table of the cabinet, or, in which the spherical cabinet is installed in a ring-like frame by means of arms projecting from both sides of the cabinet, and the like are shown in the drawings. Although such constructions may be possible for a portable type television monitor, it is thought that there is a problem of strength for a display device larger in size than a certain extent.
According to Japanese Utility Model Laid-Open No. 59-149190 (1984), a display unit is supported by a ball and socket type supporting equipment in order to be capable of tilting the whole display unit. But in such a construction, the weight of the display unit placed upside cannot be supported stable unless the ball and socket type supporting equipment is made larger than certain extent.
In view of such a matter, it is desired to provide a comparatively large-sized display device provided with a mechanism capable of rotating and tilting a screen but light, small-sized and sufficiently strong.
In addition, in a display apparatus capable of not only rotating but also tilting a screen, it becomes unstable because the weight thereof inclines toward the front portion of the display unit, and there is the possibility that the corner portions of a front face of a cabinet of the display unit come into collision with the base which supports the display unit, when the screen is intended to be rotated at a tilt angle smaller than a certain angle, that is to say under the condition that the screen is tilted at an angle smaller than a certain angle. There is the possibility that such a situation leads to an accident. In order to prevent the accident from occurring, the main body is placed on higher position, but is to be excessibly unstable due to the weight of the rolling mechanism of the screen, as described above, so a countermeasure for such an accident is required.